[She doesn't answer for a while, and when she does, her voice is gravely. She didn't sleep.]
... I had not intended to ruin your party. I am - incredibly sorry, for my behaviour.
Other options:
no subject
[She doesn't answer for a while, and when she does, her voice is gravely. She didn't sleep.]
... I had not intended to ruin your party. I am - incredibly sorry, for my behaviour.